* {
  margin: 0;
  padding: 0;
  list-style: none;
}

#main {
  padding: 20px;
}

h2 {
  text-align: center;
}

ul {
  border: red 1px solid;
  padding: 20px;
  overflow: hidden;
}

.mt10 {
  margin-top: 10px;
}

.fl {
  float: left;
}

.half {
  width: 50%;
}

input[type="button"]{
  width: 100px;
  height: 50px;
  cursor: pointer;
}